Abstract. The corona is characterized by an array of structures
of various temporal and spatial scales, each providing
a clue to its global physical properties.
These structures are intrinsically linked to the coronal
magnetic field, and range from small-scale, quickly varying
structures in the lower corona to large-scale, quasi-static
structures in the upper corona. We are interested
in using observations of the solar corona in spectral
emission and scattered white light to study the connections
between lower, smaller-scale coronal structures and large-scale
coronal ``streamer'' structures for the ascending phase of
the solar cycle. Specifically, we propose to
use observations from a variety of coronal telescopes including
SOHO/CDS, SOHO/EIT, SOHO/LASCO, SOHO/SUMER, SOHO/UVCS, YOHKOH/SXT and HAO Mauna Loa Mark 3 during the proposed
second Whole Sun Month Campaign (August 1-28, 1998 - CROT 1939). We plan to use
these data to:

compare and combine the results of density and
temperature diagnostic techniques for the upper and lower corona

use these results to motivate and constrain a
theoretical model of force balance in the coronal streamers

study the dynamic evolution of streamers over a
complete solar rotation

In so doing, we hope to gain insight into the physics
of the stable and dynamic coronal structures
which directly affect the properties of the solar wind and
its interaction with the earth.

Proposed Study

As solar maximum approaches, the
axisymmetric streamer belt disappears to be replaced by
individual streamers of finite extent
centered at various latitudes and longitudes, as
in Figure 1 . Because white light observations depend upon the
integral of coronal density along the line of sight, it is
not possible to tell from a single image whether the streamers are
centered in the plane of the sky, or whether they are projections
of streamers centered away from the edge (or limb) of the solar disk.
Multiple white-light images of streamers rotating past the
solar limb, along with on-disk lower coronal observations of their
boundaries are needed to determine streamer morphology.
Moreover, active regions will increasingly dominate the lower
corona as we move into solar maximum. We would like to study
the relation between these hot, highly structured regions and the
upper coronal streamers.

We plan to study the physical properties of a few selected
ascending phase streamers as they rotate past the solar limbs
during WSM2.
Specifically, we will try to determine for each streamer selected, using upper and lower coronal observations:

where the streamer boundaries are

how the density varies with latitude, longitude, and radius

how the temperature varies with latitude, longitude, and radius

how the streamer structure and its physical properties evolve over WSM2

We will use the results of this analysis,
particularly regarding
the thermodynamics and morphology of the streamers,
to expand upon theoretical models of the
solar minimum corona and to gain understanding about the coronal magnetic field, its role in coronal force balance, and the connections between large- and small-scale structures.

Finally, it is a distinct possibility we will observe
one of our chosen streamers blow out in a coronal mass ejection (CME).
CMEs are directly connected to occasionally damaging geomagnetic
storms. Because emission corona observations are
not limited to observations of the limb, lower coronal
signatures of CMEs would be particularly helpful for predicting
such potential disruptions of ground- and space-based systems.
(See SOHO
JOP 3 for an existing lower coronal CME study.)
Since the rate of CMEs observed in white light by SOHO is high,
and expected to increase as we move toward solar maximum, we stand
a good chance of seeing one during our study. If so, we will
have detailed information about the temperature and density profile
at the base of the streamer, as well as the white light streamer structure,
both before and after the eruption.
We could then ask,
how is the streamer morphology
changed by the CME, and does it return to its original state?
Where does the mass of the CME come from?
Is the CME heated, and if so where?
The answers to these questions would yield important constraints
on existing CME models.